Tiny BASIC programmable calculator

TB-40 is a Tiny BASIC-programmable calculator with 40 keys (hence the name), each of them having a single purpose. That limits the number of features, but also makes operation very simple.

For that to work, TB-40 gives up comments and character strings, but in return each keyword has a dedicated key. `PRINT 2 + 2 ENTER`

is literally just five keystrokes! Moreover, TB-40 supports floating point numbers, unlike the original version of the language.

Most of the time you're probably going to use TB-40 like in the above example, to compute immediate expressions, with the added ability to store intermediate values in variables. But you also have a fully working Basic interpreter, capable of running programs such as:

```
10 INPUT A , X
20 IF A > X THEN LET A = A - X
30 IF X > A THEN LET X = X - A
40 IF A <> X THEN GOTO 20
50 PRINT A
```

that gives you the greatest common divisor of two numbers by Euclid's algorithm.

A few tips:

- To delete a line of code, enter just the line number without any content.
- The CLEAR statement erases both the program and variables.
- Using RUN in a program (as opposed to interactively) will mess things up.

That's about it. Enjoy!

(Last updated: 7 August 2016)